The invention relates generally to energy storage systems in wind turbine and windfarm systems and more specifically to energy storage systems which communicate to provide for operation of wind turbines, particularly during operating conditions for which alternate power must be supplied to the wind turbine.
Wind turbines are regarded as environmentally friendly and relatively inexpensive alternative sources of energy that utilize wind energy to produce electrical power. A wind turbine generator generally includes a wind rotor having a plurality of blades that transform wind energy into rotational motion of a drive shaft, which in turn is utilized to drive a rotor of an electrical generator to produce electrical power. Modern wind power generation systems typically take the form of a wind farm having multiple such wind turbine generators that are operable to supply power to a transmission system providing power to a utility grid. Output from the wind turbine generators is typically combined for transmission to the grid.
Wind is an intermittent resource and power supplied by the wind farm to utilities is significantly influenced by changes in wind conditions. Generally, power output of a wind turbine power station increases with wind speed, until the wind speed reaches the rated wind speed for the turbine. With further increases in wind speed, the turbine operates at rated power up to a cut off value or a trip level. This is generally the wind speed at which dynamic loads on the wind turbine cause the mechanical components of the turbine to reach a fatigue limit. As a protective function, at wind speeds higher than a certain speed, wind turbines are often required to shut down, or reduce loads by regulating the pitch of the blades or braking the rotor, thereby leading to a reduced power output of the wind turbine generator, and consequently of the wind farm. However, electrical loads on utilities need to be balanced at all times by power generation units. Hence, utility systems usually have additional power generation resources available, such as thermal generators that can accommodate this variability in wind conditions.
In some configurations and referring to FIG. 1, a wind turbine 100 comprises a nacelle 102 housing a generator (not shown in FIG. 1). Nacelle 102 is mounted atop a tall tower 104, only a portion of which is shown in FIG. 1. Wind turbine 100 also comprises a rotor 106 that includes one or more rotor blades 108 attached to a rotating hub 110. Although wind turbine 100 illustrated in FIG. 1 includes three rotor blades 108, there are no specific limits on the number of rotor blades 108 required by the present invention.
Referring to FIG. 2, various components are housed in nacelle 102 atop tower 104 of wind turbine 100. The height of tower 104 is selected based upon factors and conditions known in the art. In some configurations, one or more microcontrollers within control panel 112 comprise a control system are used for overall system monitoring and control including pitch and speed regulation, high-speed shaft and yaw brake application, yaw and pump motor application and fault monitoring. Alternative distributed or centralized control architectures are used in some configurations.
In some configurations, the control system provides control signals to a variable blade pitch drive 114 to control the pitch of blades 108 (not shown in FIG. 2) that drive hub 110 as a result of wind. In the illustrated configuration, hub 110 receives three blades 108, but other configurations can utilize any number of blades. In some configurations, the pitches of blades 108 are individually controlled by blade pitch drive 114. Hub 110 and blades 108 together comprise wind turbine rotor 106.
The drive train of the wind turbine may include a main rotor shaft 116 (also referred to as a “low speed shaft”) connected to hub 110 and supported by a main bearing 130 and, at an opposite end of shaft 116, to a gear box 118. Gear box 118, in some configurations, utilizes a dual path geometry to drive an enclosed high-speed shaft. The high-speed shaft (not shown in FIG. 2) is used to drive generator 120, which is mounted on main frame 132. In some configurations, rotor torque is transmitted via coupling 122. Generator 120 may be of any suitable type, for example, a wound rotor induction generator.
Yaw drive 124 and yaw deck 126 provide a yaw orientation system for wind turbine 100. Wind vane 128 provides information for the yaw orientation system, including measured instantaneous wind direction and wind speed at the wind turbine. In some configurations, the yaw system is mounted on a flange provided atop tower 104.
In some configurations and referring to FIG. 3, a control system 300 for wind turbine 100 may include a bus 302 or other communications device to communicate information. Processor(s) 304 may be coupled to bus 302 to process information, including information from sensors configured to measure displacements or moments. Control system 300 may further include random access memory (RAM) 306 and/or other storage device(s) 308. RAM 306 and storage device(s) 308 are coupled to bus 302 to store and transfer information and instructions to be executed by processor(s) 304. RAM 306 (and also storage device(s) 308, if required) can also be used to store temporary variables or other intermediate information during execution of instructions by processor(s) 304. Control system 300 can also include read only memory (ROM) and or other static storage device 310, which is coupled to bus 302 to store and provide static (i.e., non-changing) information and instructions to processor(s) 304. Input/output device(s) 312 can include any device known in the art to provide input data to control system 300 and to provide yaw control and pitch control outputs. Instructions are provided to memory from a storage device, such as magnetic disk, a read-only memory (ROM) integrated circuit, CD-ROM, DVD, via a remote connection that is either wired or wireless providing access to one or more electronically-accessible media, etc. In some embodiments, hard-wired circuitry can be used in place of or in combination with software instructions. Thus, execution of sequences of instructions is not limited to any specific combination of hardware circuitry and software instructions. Sensor interface 314 is an interface that allows control system 300 to communicate with one or more sensors. Sensor interface 314 can be or can comprise, for example, one or more analog-to-digital converters that convert analog signals into digital signals that can be used by processor(s) 304.
FIG. 4 illustrates a prior art wind turbine system that includes a hub, a shaft coupled to the hub and a hydraulic pump disposed proximate to the shaft and configured to provide a pressurized fluid to a motor. In some configurations, the wind turbine power generation system 105 housed in nacelle 102 (FIG. 1) may be arranged as illustrated in FIG. 4. Here, a rotor 106 is coupled by a shaft 116 to a hydraulic pumping system 121. This hydraulic pumping system 121 is disclosed in U.S. patent application Ser. No. 12/409,909, filed Mar. 24, 2009, and is further disclosed in U.S. patent application Ser. No. 12/265,824, filed Nov. 6, 2008. Rotor 106 rotationally drives shaft 112 to provide mechanical energy to hydraulic pumping system 121 to circulate high pressure hydraulic fluid within the hydraulic pumping system 121. The hydraulic pumping system 121 is coupled to a motor 136 via a hydraulic fluid circulation system 125. The motor 136 converts energy from the circulating high pressure fluid into mechanical energy. The motor 136 may be any hydraulic motor suitable for this purpose that is known in the art. The motor 136 may be coupled by a transfer device 138 to a generator 120. The hydraulic pumping system 121, the motor 136 and the generator 120 may include sensors (not shown) for providing motor operational data to the power generation system 105. The transfer device 138 may be a shaft. The generator 120 converts the mechanical energy into electricity. The generator 120 provides the generated electricity to a power grid 150 via a transmission line 142. In another arrangements, the motor 136 and generator 120 may be combined in a single device.
Utility grid abnormalities may result in conditions for which the wind turbine may no longer supply power to the grid. Yet under these conditions a strong windforce may continue to drive the wind turbine to produce power. Unless the produced power is transmitted from the rotor, after a time, the wind turbine must be shut down. Further, during other wind turbine operating conditions, such as grid transients, loss of power to wind turbine operating systems or maintenance conditions, the wind turbine may either need to be supplied power for its operating systems or transfer excess power. Consequently it would be desirable to provide a variety of energy storage functions that could store energy in suitable form to subsequently deliver the energy to wind turbine operating systems that require alternate power sources under various wind turbine operating conditions, or to absorb excess energy from the wind turbine that cannot be supplied to the grid. In wind turbines, several energy storage systems may be incorporated. Some very common examples include batteries for pitch systems or for wind turbine controls or hydraulic accumulators for (secondary) brake systems. These storage systems may often stand alone. Accordingly, it may be desirable to have communicating accumulation systems and conversion systems between them.